Delineation of relationship between brain tumor and the white matter tracts by means of 3-dimenitional anisotropy contrast imaging and diffusion tensor analysis

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PURPOSE : To evalutate the usefulness of 3-dimentional anisotropy contrast (3DAC) imaging and diffusion tensor analysis for delineation of relationship between brain tumor and the white matter tracts, we applied these technique to 5 normal volunteers (first year) and 19 patients with a supratentorial brain tumor.METHODS : 3DAC imaging was performed by synthesizing color-coded diffusion-weighted images (DWI) which were obtained by applying motion probing gradient (MPG) in 3-orthogonal directions. Diffusion tensor analysis was performed using DWIs obtained by applying MPG in 6 different directions. Using this data sets, we obtained images of fractional anisotorpy (FA), apparent diffusion coefficient (ADC) trace and diffusion eigenvalues. The FA is one of the indicies representing diffusion anisotorpy.RESULTS :1) Results of 3DAC imagingIn the analysis of the normal subjects, the 3DAC images delineated the white matter tracts clearly in all cases. However, the images tended to be poor in i … More nfratentorial region due to susceptiblity artifacts, which made it almost impossible to evaluation of the fiber tracts in some cases.In the cases with brain tumor, we evaluated the relationship between a tumor and the pyramidal tract by 3DAC images. In all cases, 3DAC images could clearly show the relationship ; the tumor just compressed the tracts or the tumor/perifocal edema involved the tracts.2) Results of diffusion tensor analysisAt first, we compared the accuracy of the measurement of diffusion anisotropy between diffusion tensor analysis (FA) and conventional 3-orthogonal diffusion imaging (FA-3) in 5 normal subjects and 4 patients with brain tumor. In the analysis of healthy subjects, FA-3 was significantly more asymmetric than FA.In one case with a brain tumor compressing the pyramidal tract, FA-3 showed markedly underestimated, which led erroneous conclusion.Then, we investigated the diffusion characteristics of the pyramidal tract in cases with brain tumor. The FA, ADC trace and eigenvalues of the pyramidal tracts were measured. These indices reflected condition of pyramidal tract, being compressed and/or being T2-high. Estimation of eigenvalues, in addition to the FA and the trace, should provide more detailed information.CONCLUSION3DAC imaging and diffusion tensor analysis may provide additional useful information about the white matter tracts, which may be helpful for surgical planning of brain tumors. Less